Radio frequency (RF) receivers are used in a wide variety of applications such as radios, television receivers, cellular telephones, pagers, global positioning system (GPS) receivers, cable modems, cordless phones, and the like. As used herein, a “radio frequency” signal means an electrical signal conveying useful information and having a frequency from about 3 kilohertz (kHz) to thousands of gigahertz (GHz), regardless of the medium through which such signal is conveyed. Thus an RF signal may be transmitted through air, free space, coaxial cable, fiber optic cable, etc.
One of the problems with broadcast radio systems is the problem of signal reflection. A receiver may receive multiple versions of a transmitted signal with different strengths and phase shifts because of signal reflection through the transmission medium. These phase shifted versions can destructively interfere with the main received signal and degrade it. The problem is worse for systems such as automobile radio receivers that constantly change position relative to a fixed antenna and that will occasionally be subject to relatively strong reflected signals.
In an effort to compensate for the different signal reflection environments, engineers have developed diversity receivers. Diversity receivers receive broadcast signals using two or more antennas at different positions and/or orientations. The separately received signals are combined to provide a better output signal. One diversity receiver configuration uses multiple radio receiver chips each connected to its own separate antenna. The radio receiver chips use an inter-chip link to exchange data for combination into a final output signal.
The radio receiver chips are complex chips that may include a digital signal processor (DSP) and a general-purpose microcontroller each executing the same respective stored programs. Each radio receiver chip loads the stored programs from a single serial non-volatile memory chip into its own on-chip memory. Because it requires multiple chips, the time required for the diversity receiver to load software from the non-voltage memory into all the chips can be long, resulting in slow boot-up sequences.
In the following description, the use of the same reference symbols in different drawings indicates similar or identical items. Unless otherwise noted, the word “coupled” and its associated verb forms include both direct connection and indirect electrical connection by means known in the art, and unless otherwise noted any description of direct connection implies alternate embodiments using suitable forms of indirect electrical connection as well.